The low-carb Paleo diet is the most popular diet around today, and has a huge celebrity following, including Tim McGraw (who credits it for his jaw-dropping 40-pound weight loss), Megan Fox, Jessica Biel, Robin Wright and Joe Manganiello.

"I don't eat any toxic chemicals and I try to eat organic as often as possible," she said. "We eat a ton of veggies, chicken, grass-fed beef, bison and fish. We also love sweet potatoes and brown rice pasta."

Cavallari said her breakfast is usually a smoothie, oatmeal or eggs, while lunch is a salad or turkey sandwich. Kristin also snacks most afternoons, enjoying nuts with dried cherries, chips with hummus, or an apple with almond butter.

Kristin also tries to eat healthy Paleo-approved fats such as avocados, olive oil and coconut oil. "I love avocados with olive oil and sea salt and I put coconut oil in or on everything," she said.

Cavallari said she started working out just three weeks after her second son, Jaxon, was born (in May 2014). She exercises 30 to 45 minutes four to five days a week, focusing on toning her legs and butt.

Thanks to her hard work, Kristin is now just a couple of pounds away from her pre-baby weight. It's not surprising Cavallari lost her baby weight in record time. In 2012, she regained her slim pre-pregnancy body just three months after giving birth to son Camden.

The willowy 5-foot-6 blonde beauty previously revealed she's so obsessed with clean eating that she eats fast food just twice a year. Surprisingly, Cavallari thought she looked fat when she starred on the reality TV show "The Hills" in 2009, and slimmed down dramatically a few years ago after seeing an unflattering photo of herself. She has been a fitness fanatic ever since.

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Samantha Chang is the executive editor and co-owner of www.theimproper.com., an arts and entertainment website in New York City. A graduate of the University of Pennsylvania, Samantha enjoys running, cycling and taking photos. Contact her at schang@theImproper.com.